The Russian helicopters bound for Syria – and at the center of a US-Russia diplomatic dispute – might not make it to Syria after all.

Standard Club, a British ship insurer, terminated insurance coverage of the Russian ship purported to be carrying arms after the company heard allegations about the cargo and destination, according to Russian news outlet RIA Novosti. The Russian ship is believed to be carrying refitted combat helicopters and antiship missiles to Tartous, Syria, where Russia has a naval base. Without insurance, however, ships cannot enter port.

Russia has denied that the equipment could be used against Syrian civilians, insisting the materiel is for defensive purposes only. Russian Foreign Minister Sergei Lavrov also said that the helicopters were supplied during the Soviet-era and were merely being returned to Syria under an already existing contract, according to RIA Novosti.

Russia has been the subject of intense international criticism for its support of Syrian President Bashar al-Assad's regime and for blocking any international efforts to take stronger action.

Some Syria observers see the shipment as undermining Russia's insistence that it opposes intervention in the conflict. The Telegraph's Middle East correspondent, Richard Spencer, writes:

"Russian arguments against direct involvement could now be strongly questioned by the British and Americans: 'Who is intervening in the crisis here? Who is pouring fuel on the flames? If you are providing attack helicopters to the Syrians how can you possibly say you are not intervening in the crisis?'"

Mr. Spencer speculated that this is likely to be followed with a stepping up of Western support for the rebels, perhaps through arms supplies.

We agree to cooperate bilaterally and multilaterally to solve regional conflicts. In order to stop the bloodshed in Syria, we call for an immediate cessation of all violence and express full support for the efforts of [United Nations]/League of Arab States Joint Special Envoy Kofi Annan, including moving forward on political transition to a democratic, pluralistic political system that would be implemented by the Syrians themselves in the framework of Syria's sovereignty, independence, unity, and territorial integrity. We are united in the belief that the Syrian people should have the opportunity to independently and democratically choose their own future.

But their support for Mr. Annan's plan is no change from current positions, and the peace plan has had little effect on the violence there. The international community has largely deemed it a failure, and the UN observer mission to Syria was suspended last week out of concern for the safety.